1. Field of the Invention
The present invention relates to a zoom lens having a compact size suitable for use in a lens shutter camera, a video camera or the like and, more particularly, to a zoom lens of compact size which has a zoom ratio between approximately 2x-2.5x, appropriately corrected aberrations and a reduced overall lens length (defined as the distance between the first lens surface and the image surface).
2. Description of the Related Art
In the recent situation in which lens shutter cameras, video cameras and the like have been undergoing miniaturization, it is desired to develop a compact zoom lens whose overall lens length is reduced. In particular, in the field of compact cameras such as lens shutter cameras of the non-interchangeable lens type, there is a need for cameras provided with zoom lenses. Therefore, it is desired to develop a zoom lens whose overall length is approximately the same as that of a single-focus lens of the type which has heretofore been used in such a camera.
Various kinds of zoom lenses which include a standard angle of view (or photographic angle of view of 2.omega.=47 degrees, that is, a focal length of approximately 50 mm in terms of the angle of view of a 35-mm still camera) are proposed in, for example, Japanese Patent Publication No. 29146/1974. These kinds of zoom lenses consist of two lens groups: a front lens group of negative refractive power and a rear lens group of positive refractive power, with the front and rear lens groups being aligned in that order from the object side. Such zoom lenses are arranged so that the magnification can be varied by altering the interval distance between the front and rear lens groups. Since the negative and positive refractive powers are axially distributed in that order from the object side and a relatively long back focal length can be ensured, such zoom lenses are suitable for use in a single reflex camera. However, such conventional zoom lenses have the disadvantage that the overall lens length is excessively long relative to the overall size of a typical lens shutter camera.
To solve this problem, in the commonly assigned U.S. Pat. No. 4,682,860 (which is based on Japanese Patent Laid-open Nos. 128911/1981 and 201213/1982), the assignee has previously proposed a compact zoom lens consisting of two lens groups: a front lens group of positive refractive power and a rear lens group of negative refractive power, with the front and rear lens groups being aligned in that order from the object side. This compact zoom lens is so arranged that its magnification can be varied by altering the air separation interval between the front and rear lens groups. As disclosed in U.S. Pat. No. 4,682,860, a zoom lens of the telephoto type has the positive and negative refractive powers axially distributed in that order from the object side and a relatively short back focal length, a zoom ratio of approximately 1.5x and a reduced overall lens length.
This type of zoom lens is also described in U.S. Pat. No. 4,679,913 and Japanese Patent Laid-open Nos. 138817/1987 and 92909/1987. Japanese Patent Laid-open No. 48009/1985 (U.S. Ser. No. 643,820), Japanese Patent Laid-open No. 170816/1985, U.S. Pat. No. 4,659,186, and Japanese Patent Laid-open No. 191217/1985 disclose other related art.